This invention generally relates to torquing devices for guiding members which facilitate the advancement of intravascular catheters in procedures such as percutaneous transluminal coronary angioplasty (PTCA).
In typical PTCA procedures a guiding catheter having a preformed distal tip is percutaneously introduced into the cardiovascular system of a patient and advanced therein until the distal tip thereof is in the coronary artery. A dilatation catheter having an inflatable balloon on the distal portion thereof is advanced into the patient's coronary anatomy through the guiding catheter until the dilatation balloon is properly positioned across the lesion to be dilated. Once in position across the lesion, the balloon is inflated to a predetermined size with radiopaque liquid at relatively high pressures (e.g., greater than 4 atmospheres) to compress the atherosclerotic plaque of the lesion against the inside of the artery wall. The balloon is then deflated so that the dilatation catheter can be removed and blood flow resumed through the dilated artery.
With over-the-wire dilatation catheters, movable guidewire systems, a guidewire is first steered through the coronary anatomy and then the dilatation catheter is advanced over the guidewire until in proper position. With fixed guidewire systems, the guidewire is fixed within the catheter so that both are advanced simultaneously through the patient's coronary arteries.
Steerable dilatation catheters with fixed guiding members provide much smaller deflated profiles than conventional catheters which allows the steerable catheter to cross tighter lesions and to be advanced much deeper into the patient's coronary anatomy. Additionally, procedure time can shorten because there is no need to first advance a guidewire through the stenosis and then advance a conventional dilatation catheter over the previously placed guidewire.
Further details of dilatation catheters, guidewires, and the like for angioplasty procedures can be found in U.S. Pat. No. 4,323,071 (Simpson-Robert); U.S. Pat. No. 4,439,185 (Lundquist); U.S. Pat. No. 4,468,224 (Enzmann et al.); U.S. Pat. No. 4,516,972 (Samson); U.S. Pat. No. 4,538,622 (Samson et al.); U.S. Pat. No. 4,554,929 (Samson et al.); U.S. Pat. No. 4,582,181 (Samson); U.S. Pat. No. 4,616,652 (Simpson) and U.S. Pat. No. 4,638,805 (Powell) which are hereby incorporated herein in their entirety by reference thereto.
Typically, guidewires and guiding elements of steerable catheters have their distal ends shaped or bent by the physician before advancing these devices into the patient's vasculature. The physician then rotates or torques the proximal end of these devices, which extend out of the patient, to cause the shaped distal end to rotate so that the device can be steered to the desired vascular location even in tortuous arterial passageways. During the early periods of PCTA, the proximal end of the guidewire was merely bent into an L shape to allow the physician to more easily rotate the guidewire. It was found, however, that unlimited rotation could twist the balloon so as to interfere with the inflation and/or deflation of the balloon. Torque limiting devices were developed to control the amount of rotation to a predetermined number of rotations of the guidewire and they have met with considerable success. Details of these torquable devices can be found in U.S. Pat. No. 4,619,263 (Frisbie) and U.S. Pat. No. 4, 664,113 (Frisbie), which are hereby incorporated herein in their entirety. These torquing devices, however, were limited to one-to-one rotation between the input to the torquing knob and the output to the guidewire and usually they required both hands of the physician to properly operate which made the procedure very complicated.
What has been needed and heretofore unavailable is a torquing device which provides for a greater rotational output than the rotational input and particularly such a torquing device which could be operated with one hand by the physician who is performing the vascular procedure. The present invention satisfies this need.